Biological system models

Ochrymowycz and his coworkers have also prepared a number of polysulfur macrocycles for use in biological or biological model systems . The synthetic methodology is essentially similar to that described above except that certain of the sulfur containing fragments were prepared by addition reactions to ethylene. Two examples of this approach, taken from ref. 59, are shown in Eq. (6.9). 

Hu, C. et al., Black rice (Oryza sativa L. indica) pigmented fraction suppresses both reactive oxygen species and nitric oxide in chemical and biological model systems, J. Agric. Food Chem., 51, 5271, 2003. 

T. Ohsaka, F. Matsumoto, and K. Tokuda, An electrochemical approach to dismutation of superoxide ion using a biological model system with a hydrophobic/hydrophilic interface, in Frontiers of Reactive Oxygen Species in Biological and Medicine (K. Asaka and T. Yoshikawa, eds), pp. 91—93. Elsevier Science B.V. Oxford (1994). 

This permeability barrier shows selectivity in that small hydrophobic molecules can partition into and diffuse across the lipid bilayer of the cell membrane, whereas small hydrophilic molecules can only diffuse between cells (i.e., through the intercellular junctions). In addition, the presence of uptake and efflux transporters complicates our ability to predict intestinal permeability based on physicochemical properties alone because transporters may increase or decrease absorptive flux. The complexity of the permeability process makes it difficult to elucidate permeability pathways in complex biological model systems such as animals and tissues. For this reason, cultured cells in general, and Caco-2 cells in particular, have been used extensively to investigate the role of specific permeability pathways in drug absorption. 

The first step in progressing from in vitro mobilization experiments to clinical trials is the setting up of biological model systems (356). Next comes the testing of oral efficacy in animals such as mice, rats, and rabbits (43,249), alongside toxicity studies. We cite a few of the... 

Mitchell JH, Gardner PT, Mcphail DB et al. Antioxidant efficacy of phytoestrogens in chemical and biological model systems. Arch. Biochem. Biophys. 360, 142-148, 1998. 

Liquid Crystalline Phases in Biological Model Systems... 

Although oxo transfer allows the oxidation of enzyme substrates in biological model systems [196,198,231], the ultimate source of the oxygen incorporated by molybdenum or tungsten enzymes is water (Eq. 19). As such, in the absence of an oxygen atom donor,... 

Latour LL, Warach S (2002) Cerebral spinal fluid contamination of the measurement of the apparent diffusion coefficient of water in acute stroke. Magn Reson Med 48 478-486 Latour LL, Svoboda K, Mitra PP, Sotak CH (1994) Time-depen-dent diffusion of water in a biological model system. Proc Natl Acad Sci USA 91 1229-1233 Le Bihan D (1995) Molecular diffusion, tissue microdynamics and microstructure. NMR Biomed 8 375-386 Le Bihan D (2003) Looking into the functional architecture of the brain with diffusion MRI. Nat Rev Neurosci 4 469-480 Le Bihan D, van Zijl P (2002) From the diffusion coefficient to the diffusion tensor. NMR Biomed 15 431-434 Le Bihan D, Mangin JF, Poupon C, Clark CA, Pappata S, Molko... 

To validate interaction assays, a suitable biological model system is helpful. cAMP-dependent protein kinase (PKA) is used as such a model system in the assays described below. PKA is the main target for the second messenger cAMP in eukaryotic cells and, since it has been implicated in various human diseases, the development of cAMP analogs modulating PKA activity has provoked increasing interest. 

In this paper we have provided a brief overview of the history and state-of-the-art of marine N-cycIe modeling. Our emphasis has been on prognostic open-ocean models and coupled physical-biological model systems. There has been significant... 

The biological model system has been described in some detail previously [12]. In a typical experiment, an individual free-floating bacterium is trapped by the optical tweezers (run at low power, typically a few tenth of mW at the sample) and mounted on a large (9 pm) bead that is firmly attached to the microscope slide. A small free-floating bead (3 pm) is then trapped by the optical tweezers with normal power (a few hundreds of mW) and brought to a position close to but not in direct contact with the bacterium. The system is... 

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